var str = ADRESS.charAt(0);
var str =  /\d+/g;
if (str.typeof = number) ....

	<script>
	var poss = document.getElementById('possta').innerHTML;
	var adress = document.getElementById('adressat').innerHTML;
	var regex = /[0-9]{5}/;
	var match = adress.match(regex);
		if (poss == "" && match != "") {
			alert("sad");
		};
	</script>

<div id="test">
<table border="1">
	<tr>
		<td id="adressat">0 234 fdsdfs dfsd/ds 1</td>
		<td id="possta"></td>
	</tr>
</table>
</div>

match[0] != ""

	<script>
	var poss = document.getElementById('possta').innerHTML;
	var adress = document.getElementById('adressat').innerHTML;
	var regex = /[0-9]{5}/;
	var match = adress.match(regex);
		if (poss == "" && isNaN(match)) {
			alert("sad");
		};
	</script>

	<script>
	var poss = document.getElementById('possta').innerHTML;
	var adress = document.getElementById('adressat').innerHTML;
	var regex = /[0-9]{5}/;
	var match = adress.match(regex);
		if (poss == "" && !isNaN(match)) {
			alert("sad");
		};
	</script>

poss.innerText = "test";

possta.innerHTML = "test";

possta.innerText = "test";

<script text="javascript">
      var adressat = document.getElementById("adresa").innerHTML;
      var poss = document.getElementById("posta1").innerHTML;
      var regex = /[0-9]{5}/;
      var match = adressat.match(regex);
           if (poss == "" && match != null) {
               posta1.innerHTML = '||SUBSTR(ent.adress,1,1)||';
               posta2.innerHTML = '||SUBSTR(ent.adress,2,1)||';
               posta3.innerHTML = '||SUBSTR(ent.adress,3,1)||';
               posta4.innerHTML = '||SUBSTR(ent.adress,4,1)||';
               posta5.innerHTML = '||SUBSTR(ent.adress,5,1)||';
           }
</script>